Last week, one of the most unusual smartphone accessories to be dreamed up in recent memory made its presence known in a big way. Rumors back in June suggested that Sony might be working on some manner of add-on camera system for smartphones, featuring a fully integrated lens and sensor design that attached to an existing handset’s back and communicated with the phone wirelessly. That sounded like the kind of neat idea that some engineer thinks up, it gets kicked around a few meetings, and is ultimately dismissed out of a desire to focus on more mainstream products.

But this time the rumors didn’t go away, and a pair of leaks sure made the case that not only was Sony going ahead with this project, but that there might even be two such models produced. I’m still not 100% certain that this isn’t an elaborate hoax, but with each new leak that arrives, I’m more and more buying that Sony really intends to launch these guys at the IFA next month.

With leaks moving beyond just a few pictures and now ultimately delivering some hard technical data from user manuals, I’m finding myself better able to get a sense for this hardware and just how it will work, but at the same time I’m growing less and less enamored with it. While the initial idea sounded like an elegant solution to the problem of smartphone camera quality, I’m hard-pressed to understand just whom this is for, and worry that add-ons in general are never going to be the right answer to the smartphone camera question.

The one thing last week’s leaks really drove home for me was just how substantial these “lens cameras” will be. With diameters just under 2.5 inches, we’re looking at accessories nearly as wide as smaller phones. The two models we’ve heard about should have masses of 105 and 179 grams, figures that already run the gamut for the sort of bulk we expect from smartphones themselves.

My takeaway from this: these accessories are just a little too big to comfortably shove in your pocket. Even the thinnest one is about 1.3 inches deep, substantially thicker than a hockey puck.

So despite good intentions of delivering the quality of a stand-alone camera while not requiring users to lug around a separate device alongside their smartphones, that’s exactly what Sony is going to end up making users do. It’s not that it needs a LOT of extra space, but merely having to think about where you’ll stow it, and remembering to bring it along when you’ll be snapping pics, seems to run counter to the idea of replacing your camera with a smartphone that just does everything.

I guess the closest analogy I can draw is to devices like the Jawbone Jambox: yes, it does exactly what it sets out to do, and improves the experience you get from your smartphone, but it doesn’t fix any problems with why our phones aren’t delivering the well-rounded experiences we wish they did in the first place. It’s a Band-Aid. And just like with these lens-cameras, it’s more crap to lug around with you.

But there’s hope. Some companies are taking bold steps with audio to improve the on-phone experience (just as others are doing with imaging) so we don’t have to rely on bulky add-ons; just look at HTC’s new love affair with front-facing stereo speakers. That’s what we need: investments in making the out-of-the-box experience superior.

Granted, there’s still much we don’t know about these Sony cameras. Price is one of my big concerns, and I would not be shocked to see these sell for nearly as much as phones themselves. That could easily be these products’ undoing, and I wouldn’t be surprised if many purchasers end up kicking themselves, wondering why they didn’t just drop another hundred or so on a fully stand-alone camera to complement their smartphones. After all, plenty of modern cameras can talk over WiFi, and Sony even has models with NFC support, just begging to be used with smartphones.

In the end, I see this effort failing on multiple fronts. Sony’s still not finding a way to leverage its camera prowess to provide the best smartphone camera experience around (prove me wrong, Honami!) – and it must be nothing less than embarrassing that Nokia’s been able to utterly trounce the company in that field. Sony’s not giving users a compelling excuse to ditch their stand-alone cameras, and instead this feels like a less useful version of a point-and-shoot.

I may end up eating my hat, and these lens-cameras will wow in a way I’ve yet to anticipate, but looking at what we’ve seen so far I’ve got just one word to describe these accessories: impractical.